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Commit 67147e96 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
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s390/stack: fix possible register corruption with stack switch helper



The CALL_ON_STACK macro is used to call a C function from inline
assembly, and therefore must consider the C ABI, which says that only
registers 6-13, and 15 are non-volatile (restored by the called
function).

The inline assembly incorrectly marks all registers used to pass
parameters to the called function as read-only input operands, instead
of operands that are read and written to. This might result in
register corruption depending on usage, compiler, and compile options.

Fix this by marking all operands used to pass parameters as read/write
operands. To keep the code simple even register 6, if used, is marked
as read-write operand.

Fixes: ff340d24 ("s390: add stack switch helper")
Cc: <stable@kernel.org> # 4.20
Reviewed-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 9e3d62d5
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